Significant Accounting Policies - Schedule rollforward of the allowance for credit losses for accounts receivable, notes receivable and other assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2021	Mar. 29, 2020
Allowance for Credit Loss
Current period (credit) provision for expected credit losses	$ (1,098)	$ 768
Accounts Receivable
Allowance for Credit Losses
Balance at beginning of period	3,622
Current period credit for expected credit losses	(307)
Write-offs charged against the allowance	(978)
Balance at end of period	2,337
Notes Receivable
Allowance for Credit Losses
Balance at beginning of period	3,211
Current period credit for expected credit losses	(531)
Write-offs charged against the allowance	(843)
Recoveries collected	(260)
Balance at end of period	$ 1,577